Numerical simulation of bidirectional compression molding of binary composite powder particles

Powder metallurgy is a cornerstone of advanced manufacturing and faces research challenges in achieving fully densified and homogeneous microstructures, especially for composites with different compositions. The study of the micromechanics controlling particle rearrangement and plastic deformation during compaction is crucial but is often hindered by the complexity of multi-particle interactions and size distribution effects. An efficient and accurate multi-particle finite element framework is developed herein for the explicit simulation of bidirectional die compaction in bimodal Cu–Al composite powders with controlled particle size distribution. Simulations employing a coupled discrete element method–finite element method approach encompass Cu–Al particle size ratios ranging from 1:2 to 1:5 and aluminum contents between 15 and 40 wt. %. It is found that particle size gradients dominate early densification and increasing the Cu–Al size ratio from 1:2 to 1:5 increases the initial relative density by 12.3% due to the effective filling of voids by fine Cu particles. Rearrangement driven by this size difference significantly reduces the pore volume to below 200 MPa. Increasing aluminum content from 15 to 40 wt. % enhances average relative density by 8.7% but reduces von Mises stress by 31%, governed by Al’s dominant plastic deformation. Stress concentration persists in Cu particles, characterized by parallel-aligned contact normal forces forming rigid force chains. This paper also describes different deformation mechanisms: Al particles exhibit concave plastic flow that disrupts the stress network and fills the intergranular voids, while Cu particles experience limited deformation. A particle size ratio >1:3 reduces Al deformation but reduces contact forces by 18%–22%.